My definition is someone who has no interest in the principle(s) of a particular forum, yet posts mainly for the purpose of
1) Arguing
2) Irrating others who have a different philosophy/viewpoint than theirs
3) Trying to invalidate what the other folks on the forum believe in.

For example, a troll could be someone who is super gung-ho primal and posts a bunch of stuff on vegan forums about how everything they do and think is wrong, etc...or a vegan posting a bunch of studies on this site about how red meat causes heart attacks.

Trolls have no interest in actually debating a topic, they mainly just want to piss people off and often revert to using cheap tactics to sidestep having to answer any legitimate questions.

You don't seem to understand what a troll is:
A troll is somebody that deliberately posts things that others will find offensive or have a negative emotional response to. Making a satirical/joke post is not trolling, insulting somebody is not trolling, posting a dissenting opinion is not trolling, and as a troll, you do not have believe the things you say. Thus arguing with a troll is the wrong thing to do, you are validating their posts and playing their game.
Ignoring trolls the only solution.

You don't seem to understand what a troll is:
A troll is somebody that deliberately posts things that others will find offensive or have a negative emotional response to. Making a satirical/joke post is not trolling, insulting somebody is not trolling, posting a dissenting opinion is not trolling, and as a troll, you do not have believe the things you say. Thus arguing with a troll is the wrong thing to do, you are validating their posts and playing their game.
Ignoring trolls the only solution.

are you certain about that? it would seem you lack the ability of persuasion and influence then